Objective:To explore solutions to the "grey zone" of activated partial thromboplastin time (APTT) mixing study, and establish the clinical application pathway of it.Methods:Patients treated in West China Hospital of Sichuan University from January 1, 2018, to December 31, 2019, with a prolonged APTT were included in this study. The ROC curve was used to analyze the"cut-off"of different methods and explore solutions to the "grey zone" by combination of the 1∶1 and 4∶1 mixing study. Similar samples from January 1, 2020 to December 31, 2020 were included to verify the diagnostic efficiency of the clinical application pathway.Results:The traditional Rosner index criterion had a low diagnostic accuracy in differentiating factor deficiencies from inhibitors. A total of 49 cases (15%) in the establishment group and validation group were located in the "grey zone". The optimal cut-off value of the Rosner index in our 1∶1 mixing study for determining factor deficiency was 5.0%, and inhibitor was 9.1%. The sample between 5.0% and 9.0% needed 4∶1 mixing studies, which could significantly improve the detection sensitivity of inhibitors. The percentage of extended time after incubation-P (1∶1 mixing>10.8% and 4∶1 mixing>13.5%) was better than the traditional criterion mentioned by"consensus"in determining whether the inhibitor was time-dependent. The sensitivity, specificity, positive predictive value and negative predictive value of combined the 1∶1 and 4∶1 mixing study in differentiating factor deficiencies from inhibitors all attained more than 90%. Only 7% (3/43)of inhibitors were incorrectly classified into the factor deficiency group by the combination, which was 20.9% (9/43) by traditional criterion. The specificity for detecting time-dependent inhibitor was increased from 54.2% to 100%, and accuracy was increased from 63.3% to 97.4%.Conclusions:The combination of 1∶1 and 4∶1 mixing study can better resolve the "grey zone". The established clinical application pathway is beneficial for the further promotion and clinical application of APTT mixing study.

Objective:To establish autoverification rules for coagulation tests in multicenter cooperative units, in order to reduce workload for manual review of suspected results and shorten turnaround time (TAT) of test reports, while ensure the accuracy of results.Methods:A total of 14 394 blood samples were collected from fourteen hospitals during December 2019 to March 2020. These samples included: Rules Establishment Group 11 230 cases, including 1 182 cases for Delta check rules; Rules Validation Group 3 164 cases, including 487cases for Delta check; Clinical Application Trial Group 77 269 cases. Samples were analyzed for coagulation tests using Sysmex CS series automatic coagulation analyzers, and the clinical information, instrument parameters, test results, clinical diagnosis, medication history of anticoagulant and other relative results such as HCT, TG, TBIL, DBIL were summarized; on the basis of historical data, the 2.5 and 97.5 percentile of all data arranged from low to high were initially accumulated; on the basis of clinical suggestions, critical values and specific drug use as well as relative guidelines, autoverification rules and limits were established.The rules were then input into middleware, in which Stage I/Stage II validation was done. Positive coincidence, negative coincidence, false negative, false positive, autoverification pass rate, passing accuracy (coincidence of autoverification and manual verification) were calculated. Autoverification rules underwent trial application in coagulation results reports.Results:(1) The autoverification algorisms involve 33 rules regarding PT/INR, APTT, FBG, D-dimer, FDP,Delta check, reaction curve and sample abnormalities; (2)Autoverification Establishment Group showed autoverification pass rate was 68.42% (7 684/11 230), the false negative rate was 0%(0/11230), coincidence of autoverification and manual verification was 98.51%(11 063/11 230), in which positive coincidence and negative coincidence were respectively 30.09% (3 379/11 230) and 68.42%(7 684/11 230); Autoverification Validation Group showed autoverification pass rate was 60.37%(1 910/3 164), the false negative rate was 0%(0/11 230), coincidence of autoverification and manual verification was 97.79%(3 094/3 164), in which positive coincidence and negative coincidence were respectively 37.42%(1 184/3 164) and 60.37%(1 910/3 164); (3) Trialed implementation of these autoverification rules on 77 269 coagulation samples showed that the average TAT shortened by 8.5 min-83.1 min.Conclusions:This study established 33 autoverification rules in coagulation tests. Validation showedthese rules could ensure test quality while shortening TAT and lighten manual workload.